1. Field of the Invention
The invention in general relates to signal and/or power coupling devices, and more particularly to one of the inductive coupler variety.
2. Description of the Prior Art
Inductive couplers for coupling power from a source to a load are used in environments where the ambient medium dictates against normal exposed metal-to-metal contact. For example, such couplers are utilized to prevent sparks in an explosive atmosphere and find a wide use in the off-shore oil industry or other underwater operations for making circuit-to-circuit connections beneath the surface of the water.
The inductive coupler device is based upon the alternating current transformer principle, that is, by means of electromagnetic induction a voltage is induced from a primary winding to a secondary winding with the aid of a magnetic circuit without making any physical electrical connections. In its simplest form, one type of inductive coupler utilizes two C cores representing a magnetic circuit each having a respective winding and when the respective end sections of the two C cores are brought together, a basic transformer is formed. With the application of proper electrical insulating and corrosion protecting materials, the connector may be utilized as the electrical interface between submerged components.
When utilized for signal or data transfer, these face-to-face couplers if separated by a relatively small gap exhibit an unacceptable degradation of overall frequency response.
Another type of coupler such as described in British Pat. No. 1,366,134 has been propsed for power transfer and is made up of an outer magnetic section with a winding, into which is coaxially located an inner magnetic circuit with a winding. A source of electrical power is connected to the outer winding, which constitutes a primary, and a load circuit is connected to the inner winding constituting a secondary. With such arrangement, when the inner winding is removed, the primary current increases to such an extent that a plug part must be inserted into the open socket from which the inner section was removed so as to prevent the primary circuit from burning out. Alternatively, it is proposed to provide a complete auxiliary electric circuit comprised of a plurality of inductive and capacitive elements so as to form a tuned circuit with the primary winding. Thus when the secondary is removed upon decoupling, the circuitry becomes detuned such that the primary current is appreciably lowered.
The present invention is of this coaxial variety and completely eliminates the need for auxiliary plugs or auxiliary electrical circuit components required for a tuned circuit.
Another type of coaxial coupler utilizes primary and secondary coaxial windings inductively coupled to one another without the benefit of a closed magnetic core circuit. Although power in such couplers is provided to the inner winding constituting a primary, there is very poor coupling and the design is relatively inefficient.
Still other types of coaxial couplers which include closed magnetic circuits have mating tapered surfaces. When utilized in an underwater environment, where dirt, algae, and marine growth for example may contact the surfaces of the mating parts, proper operation is severely degraded due to axial misalignment.
The coaxial coupler of the present invention is of such design to allow for a relatively high degree of axial misalignment while still maintaining proper operation for not only power transfer but for data transfer. Further, the structure of the coupler is such as to facilitate coupling and uncoupling even in an underwater environment where visibility may be impaired.